Forage harvesters are mobile machines designed to chop whole corn plants into small pieces to be fed to cattle and other livestock. Conventional forage harvesters are manufactured with a cutterhead formed with spiraled knives and rotate about a horizontal axis to chop forage material, such as corn or alfalfa, into small pieces that are typically fermented through a process referred to as ensilage. The forage harvester first severs the plants from the ground and conveys the severed plants into the path of the rotating cutterhead. By manipulating the speed at which the crop material is conveyed and the speed at which the cutterhead is rotated, the length of the small pieces of crop material can be varied as desired by the operator.
Forage harvesters can also utilize a pair of counter rotating processing rolls which rotate about parallel axes and define a gap therebetween. The crop material can pass through this gap after being chopped into small pieces by the rotating cutterhead to crack the kernels of corn that may be in the flow of crop material exiting the cutterhead. By cracking the corn kernels, livestock, particularly dairy cattle, have improved digestibility, and produced more and higher quality milk. The crop material discharged from between the corn processing rolls is fed into a blower that moves the chopped crop material through a discharge chute to be deposited into a container, such as a forage wagon that s typically connected to the forage harvester and trails behind the harvester to receive the chopped crop material. Once filled, the forage wagon is disconnected and taken to a storage facility where the forage wagon s emptied and returned to the forage harvester for refilling.
Conventional corn processing rolls are constructed with longitudinally extending grooves machined into the rolls, which are then reduced to individual teeth by a continuous spiral groove that is machined around the circumference of the roll to form peaks and valleys along the longitudinal, axial length of the outer circumferential surface of the corn processing rolls. In cross-section, these peaks and valleys can resemble saw teeth.
Due to the high cost of forage harvesters and limited harvesting time when the crop is ready to be harvested, harvesting speed is very critical to a successful operation of the forage harvester. One of the known limitations on the harvesting speed in forage harvester configurations that utilize corn processing rolls is the operating speed of the corn processing rolls. With increasing harvesting speeds being demanded of the operation of forage harvesters, the corn processing rolls require advance design to prevent the corn processing rolls from being a bottleneck in the operation of a forage harvester.
Known prior art machines have attempted to overcome this limitation by running the corn processing rolls at higher speeds, but have had limited success because of centrifugal force limits on the rolls and speed limitations on the bearings rotatably supporting the corn processing rolls. Another known prior art approach to increasing operating speeds approach has been to space the peaks on the roll surfaces farther apart, but this technique results in some kernels passing between the corn processing rolls without being cracked.
A representative example of the design of corn processing rolls for use in a forage harvester is disclosed in U.S. Pat. No. 8,480,019, granted on Jul. 9, 2013, to Bob A. Scherer, et al, in which the corn processing roll is formed with a series of longitudinally spaced grooves that define elongated axially aligned ridges between the longitudinal grooves. The corn processing roll then goes through a subsequent manufacturing process to form a spiraled groove extending circumferentially around the corn processing roll, as is best seen in FIG. 4. The longitudinal and spiral grooves disclosed in the '019 patent are formed with a v-shaped bit that creates corresponding V-shaped grooves, resulting in discrete teeth around the circumference of the corn processing roll that have a larger base than the top portion of the respective tooth, as is best seen in FIG. 5 of the '019 patent.
Corn processing rolls have been manufactured by Horning Manufacturing, LLC, for many years in a variety of configurations, including corn processing rolls with longitudinal and spiral grooves similar to that of the '019 patent, but formed with a rounded bit that creates vertical sides of the respective teeth around the circumference of the corn processing rolls. Certain configurations of the Horning Manufacturing, LLC, corn processing rolls have also been operated at differential speeds of rotation to provide a more aggressive shredding of the crop material being chopped by the forage harvester
These corn processing rolls, such as is represented in the '019 patent, formed with a spiral groove around the circumference, irrespective of the shape of the grooves, have a tendency to urge the movement of the crop material passing between the crop processing rolls toward the end of the corn processing rolls that faces the leading slope of the spiral groove. In other words, the spiral fighting of the circumferential groove pushes crop material toward the leading end of the rolls. While the leading slope of the circumferential spiral is not very aggressive, there has been sufficient movement of the crop material toward the leading end to cause more failures for the hearings supporting the rotation of the corn processing rolls at the leading end than occur at the trailing end.
It would be desirable to provide a configuration of corn processing rolls for use in forage harvesters that would facilitate the high speed harvesting operation of forage harvesters without sacrificing quality of operation. It would also be desirable to provide a configuration for corn processing rolls that would not overly stress the bearings on one end of the corn processing roll as compared with the opposing end of the corn processing roll.